We do a lot of it, but over water in deserted bays for better views of POI. Coupla three lessons from that.
Spotting ball impact is tough waaaay out there, and you need to be able to see impact to adjust your sight picture.... That is unless you're using adjustable sights and can do lots of fiddling before taking on a 300 yard mark.
Gongs will be your friend at 300, as well as lots of dry ground nearby so you can see where you're hitting.
Any little wind, the tiniest breeze even, is going to give you detailed instruction in "Kentucky windage". Man can those balls move left and right. But a wind at your back or in your face is going to affect POI as well.
Simply lining up low traditional sights as usual and raising the gun to compensate for drop is problematic unless you have a bunch of fixed aiming points above the target.
We've found it's lots better to shoot "Elmer Keith handgun style" by raising the front sight above the rear sight. He went so far as marking off the rear face of his revolvers' front sights, just so he could have a reference point where to put the rear sight while putting the front sight right on the target.
Tried it, and it's pretty darned smart. In fact it's the only way I can effectively shoot long range with fixed sights. Of course, at 300 yards, my reference point isn't even on the front sight! I use typist's "white out" to put marks on the barrel. Best I recall, with 50 caliber ball the mark is best about 6" back up the barrel from the front sight. Line up the top of the rear sight with the white mark, then set the target on top of the front sight.
Hitting low? Scratch off the white out with your thumbnail and put another a little further back down the barrel. Hitting high? Scratch off the white mark and put another on the barrel a little closer to the front sight.
I bet you and your little bottle of white-out can pin back the ears of anyone else using low traditional sights "correctly." That is.... Long as the wind isn't blowing too hard! :rotf: